C# conditional lambda instead of if statements. Value cannot be null error -


i error: system.argumentnullexception: value cannot null. point right? if .freeamount null should check in amountlist selected amount. fails doing so. can't see have done wrong here.

var amount = string.isnullorempty(formmodel.freeamount)   ? formmodel.amountlist       .where(x => x.selected)       .select(a => a.value)       .singleordefault()   : formmodel.freeamount;

you system.argumentnullexception in code posted if both freeamount , amountlist null. if there other default value want use in case, like:

var amount = string.isnullorempty(formmodel.freeamount)     ? formmodel.amountlist == null         ? "default value if freeamount , amountlist null"         : formmodel.amountlist             .where(x => x.selected)             .select(a => a.value)             .singleordefault()     : formmodel.freeamount;

otherwise, if want return null in case (which suppose more likely, since that's possibility singleordefault) can use null-conditional operator (?.):

var amount = string.isnullorempty(formmodel.freeamount)     ? formmodel.amountlist? // <-- '?' return null if amountlist null         .where(x => x.selected)         .select(a => a.value)         .singleordefault()     : formmodel.freeamount;

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